OK time for a new rear end suggestions

[Nativefx]

Well I got my correct rear Forgeline wheels in and had the tires mounted. It's now time for me to pull out the stock rear in my 69 Firebird and start fitting the 19 x 11.5 wheels with 325/30/19 Pilot Super Sports inside the Alston mini tubbed rear. So my next purchase will obviously be a new shortened rear end and I'm hoping I can get some help in deciding what to go with (12 bolt, 9") possible gearing options and differential (tru track, wavetrack, etc)? Is it worth considering a floating rear end and if so what would be the best bang for the buck?

Obviously I dont' have much knowledge about a lot of this, so maybe it would be a good idea share some of the things I do know, or at least have a fairly good idea about.

So here's some information about my setup:

Ridetech Level 2 AirRide
Motor will be swapped out later for a LS3 - roughly 480-500hp depending on cam choice (GM Hot Cam or LS7 cam, possibly others)
Trans will be swapped for T56 Magnum (thinking close ratio would be best?)
Tire size as mentioned 325/30/19 - can't remember what that calculated out to for overall height?
Front brakes are Baer Pro+ 14" so was hoping to possible match for the rear. Is this possible with a floater rear end option?

This car will be mainly a street car, but I would like the option of one day maybe doing some road racing and/or autox. Probably not a lot, so mostly street driven. Although I want it to be fun around town, i'm building this car as a driver and anticipate taking it out on a few road trips, so it would be great when considering the rear gearing to hear some thoughts on that. Right now I'm leaning towards 3.73 or 3.40. I'm still trying to read up on that aspect in relation to the T56 I go with.

I'm open to hear as many suggestions as people have, as at least I still have some flexibility in my overall setup since I haven't yet sourced the trans and motor, but I do have a pretty good idea of what it will be.

If I've let out any information necessary to provide, please let me know.